Remove commit linter

Summary: Ref T7674. This linter doesn't make sense without commit hooks.

Test Plan: N/A

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T7674

Differential Revision: https://secure.phabricator.com/D12697